Various material handling techniques are widely used for removing devices from a conveyor system in a selected order. U.S. Pat. No. 3,612,250 discloses a recirculating conveyor system for distributing address coded packages to marshalling areas. U.S. Pat. No. 3,622,000 discloses a system for removing poultry within certain weight ranges from a conveyor line, and U.S. Pat. No. 3,880,298 discloses an endless loop conveyor with tiltable article carrying trays. Special material handling problems are encountered, however, for the efficient sorting and arranging of items randomly placed on a conveyor system for distribution in a preselected order at multiple output stations along the conveyor. The commercial laundry industry has long experienced this problem, since garments which are bulk cleaned and dried must be sorted and arranged in a selected order for pickup or delivery to customers. Significant problems are encountered in satisfying the requirements of this industry, as noted below.
U.S. Pat. No. 1,217,988 discloses one early prior art technique for sorting washed laundry. Laundry is tagged and placed on a conveyor which passes a plurality of collecting stations, and a particular garment is dropped from the conveyor to a selected station in response to a trip device. Other sorting and assembling apparatus is disclosed in U.S. Pat. Nos. 1,808,405, 1,808,406 and 2,362,638, although each of these systems is not practical since a collection station is required for each customer's items U.S. Pat. No. 4,114,538 discloses a power and free conveyor system for sorting garments, and U.S. Pat. No. 4,036,365 discloses a conveyor system wherein garments are identified then dropped at a station.
U.S. Pat. No. 4,239,435 is a more recent attempt to satisfy the requirements of the commercial laundry industry for sorting and arranging garments. According to the '435 Patent, garments randomly placed on a conveyor are releasably supported thereon as the conveyor moves along its closed loop path past a plurality of receiving stations. Each receiving station identifies each garment passing thereby, and a particular garment is released from the conveyor at a particular receiving station by a special releasing device, which is controlled by a rotary solenoid responsive to the garment identifying device. The apparatus used according to this patent is complex and expensive, and the technique disclosed in this patent has found little acceptance in the commercial laundry or the industrial uniform rental industry.
Most commercially cleaned garments include a conventional identification marking affixed thereon, or can be easily identified by such an identification tag temporarily secured to the garment. These garments are, however, almost universally sorted by a manual operation. Typically, garments are first manually sorted and placed on a selected conveyor from a group of conveyors which represents a particular route which serves various customers. Once garments have been sorted by route, the garments are then similarly manually sorted and placed on a particular conveyor from a second group of conveyors representing a particular customer's account. A third manual sorting operation is required to then manually sort all garments for that particular customer, so that garments for a particular employee will be arranged together, and preferably will be in a selected sequence with respect to garments for other employees of that customer. Finally, some customers wish to have the garments for each employee arranged in a preselected sequence, i.e., shirts first, slacks second, jackets third, so that additional manually sorting operations are required.
Although almost universally used, manual garment sorting as described above has a number of significant drawbacks. First, the accuracy of any manual sorting procedure is a function of human frailties, which in turn means that sorting accuracy is influenced by considerations outside of the control of the commercial laundry employer. Extremely high sorting accuracy is required, since the cost of replacing one cleaned garment improperly sorted and delivered to the wrong customer can practically offset the profits otherwise realized by the commercial laundry for cleaning and properly sorting one hundred other garments. Apart from garment replacement costs, the goodwill of the laundry is directly connected to returning the proper garments to each customer or its employee. Second, manual sorting of garments is labor intensive and thus expensive. Moreover, in view of the number of repeated sorting operations and the multiplicity of conveyors required for each sorting operation, a good deal of floor space is required to perform the manual sorting operation. Manual sorting of garments, by its very nature, does not allow for a high level of control by the commercial laundry establishment, does not provide the laundry or its customers with desired data useful for various management reports, and is both expensive and unreliable.
Another problem with automated sorting of laundered garments concerns the reliability of retrieving the selected garment from a conveyor system at a desired time and location. Individual garments are commonly placed on individual metal wire hangers which are supported on the conveyor, and particular hangers are thus removed from the conveyor system to release the garment. According to the techniques disclosed in U.S. Pat. No. 4,239,435, each hanger is releasably supported on the conveyor system, and a carrier assembly with a swingable latch member releases a hanger to allow the hanger and garment to fall by gravity onto a guide bar. One of the primary reasons that this technique has not been widely accepted in the industrial uniform rental industry relates to the system's mechanically complex technique for removing garments from the conveyor. Other prior art devices for selectively gripping an object are disclosed in U.S. Pat. Nos. 3,425,732, 4,537,557, and 4,595,333. The systems disclosed in these patents are not, however, well-suited for gripping a metal wire hanger supporting a garment.
Reliance upon frictional engagement of a metal wire hanger with a gripper member used to remove a hanger and garment from a conveyor is not preferred, because the hanger may slip out of the gripper due to insufficient holding force. The required frictional holding force is a function of varying inertia forces resulting from starting and stopping movements of the garment, and varying loads caused by different garment weights. Moreover, increasing the frictional gripping force on a garment hanger increases maintenance due to increased stress forces, and can damage or break the hanger.
The disadvantages of the prior art are overcome by the present invention, and improved methods and apparatus are hereinafter disclosed for efficiently sorting and arranging items, and particularly clothing garments supported by hangers, carried by and randomly positioned on a conveyor system.